Expose memory mapping; Add optional memfile dump

Author: ValentaTomas

.tool-versions

@@ -0,0 +1 @@
+rust 1.85.0

src/firecracker/src/api_server/mod.rs

@@ -274,7 +274,7 @@ mod tests {
             Box::new(VmmAction::CreateSnapshot(CreateSnapshotParams {
                 snapshot_type: SnapshotType::Diff,
                 snapshot_path: PathBuf::new(),
-                mem_file_path: PathBuf::new(),
+                mem_file_path: Some(PathBuf::new()),
             })),
             start_time_us,
         );
@@ -287,7 +287,7 @@ mod tests {
             Box::new(VmmAction::CreateSnapshot(CreateSnapshotParams {
                 snapshot_type: SnapshotType::Diff,
                 snapshot_path: PathBuf::new(),
-                mem_file_path: PathBuf::new(),
+                mem_file_path: Some(PathBuf::new()),
             })),
             start_time_us,
         );

src/firecracker/src/api_server/request/snapshot.rs

@@ -139,7 +139,7 @@ mod tests {
         let expected_config = CreateSnapshotParams {
             snapshot_type: SnapshotType::Diff,
             snapshot_path: PathBuf::from("foo"),
-            mem_file_path: PathBuf::from("bar"),
+            mem_file_path: Some(PathBuf::from("bar")),
         };
         assert_eq!(
             vmm_action_from_request(parse_put_snapshot(&Body::new(body), Some("create")).unwrap()),
@@ -153,7 +153,7 @@ mod tests {
         let expected_config = CreateSnapshotParams {
             snapshot_type: SnapshotType::Full,
             snapshot_path: PathBuf::from("foo"),
-            mem_file_path: PathBuf::from("bar"),
+            mem_file_path: Some(PathBuf::from("bar")),
         };
         assert_eq!(
             vmm_action_from_request(parse_put_snapshot(&Body::new(body), Some("create")).unwrap()),

src/firecracker/swagger/firecracker.yaml

@@ -990,6 +990,32 @@ definitions:
       vmm_version:
         description: MicroVM hypervisor build version.
         type: string
+      memory_regions:
+        type: array
+        description: The regions of the guest memory.
+        items:
+          $ref: "#/definitions/GuestMemoryRegion"
+
+  GuestMemoryRegionMapping:
+    type: object
+    description: Describes the region of guest memory that can be used for creating the memfile.
+    required:
+      - base_host_virt_addr
+      - size
+      - offset
+      - page_size
+    properties:
+      base_host_virt_addr:
+        type: integer
+      size:
+        description: The size of the region in bytes.
+        type: integer
+      offset:
+        description: The offset of the region in bytes.
+        type: integer
+      page_size:
+        description: The page size of the region in pages.
+        type: integer
 
   Logger:
     type: object

src/vmm/src/persist.rs

@@ -171,7 +171,10 @@ pub fn create_snapshot(
 
     snapshot_state_to_file(&microvm_state, &params.snapshot_path)?;
 
-    snapshot_memory_to_file(vmm, &params.mem_file_path, params.snapshot_type)?;
+    // Dump memory to file only if mem_file_path is specified
+    if let Some(ref mem_file_path) = params.mem_file_path {
+        snapshot_memory_to_file(vmm, mem_file_path, params.snapshot_type)?;
+    }
 
     Ok(())
 }

src/vmm/src/rpc_interface.rs

@@ -646,9 +646,17 @@ impl RuntimeApiController {
             GetVmMachineConfig => Ok(VmmData::MachineConfiguration(MachineConfig::from(
                 &self.vm_resources.vm_config,
             ))),
-            GetVmInstanceInfo => Ok(VmmData::InstanceInformation(
-                self.vmm.lock().expect("Poisoned lock").instance_info(),
-            )),
+            GetVmInstanceInfo => {
+                let locked_vmm = self.vmm.lock().expect("Poisoned lock");
+
+                let mut instance_info = locked_vmm.instance_info();
+
+                instance_info.memory_regions = locked_vmm
+                    .vm
+                    .guest_memory_mappings(&VmInfo::from(&self.vm_resources));
+
+                Ok(VmmData::InstanceInformation(instance_info))
+            }
             GetVmmVersion => Ok(VmmData::VmmVersion(
                 self.vmm.lock().expect("Poisoned lock").version(),
             )),
@@ -1150,7 +1158,7 @@ mod tests {
             CreateSnapshotParams {
                 snapshot_type: SnapshotType::Full,
                 snapshot_path: PathBuf::new(),
-                mem_file_path: PathBuf::new(),
+                mem_file_path: Some(PathBuf::new()),
             },
         )));
         #[cfg(target_arch = "x86_64")]

src/vmm/src/vmm_config/instance_info.rs

@@ -2,6 +2,7 @@
 // SPDX-License-Identifier: Apache-2.0
 use std::fmt::{self, Display, Formatter};
 
+use crate::vstate::vm::GuestMemoryRegionMapping;
 use serde::{ser, Serialize};
 
 /// Enumerates microVM runtime states.
@@ -46,4 +47,6 @@ pub struct InstanceInfo {
     pub vmm_version: String,
     /// The name of the application that runs the microVM.
     pub app_name: String,
+    /// The regions of the guest memory.
+    pub memory_regions: Vec<GuestMemoryRegionMapping>,
 }

src/vmm/src/vmm_config/snapshot.rs

@@ -44,7 +44,9 @@ pub struct CreateSnapshotParams {
     /// Path to the file that will contain the microVM state.
     pub snapshot_path: PathBuf,
     /// Path to the file that will contain the guest memory.
-    pub mem_file_path: PathBuf,
+    /// If not specified, the memory is not dumped to a file.
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub mem_file_path: Option<PathBuf>,
 }
 
 /// Stores the configuration that will be used for loading a snapshot.

src/vmm/src/vstate/vm.rs

@@ -27,6 +27,20 @@ use crate::cpu_config::templates::KvmCapability;
 use crate::utils::u64_to_usize;
 use crate::vstate::memory::{Address, GuestMemory, GuestMemoryMmap, GuestMemoryRegion};
 
+/// Describes the region of guest memory that can be used for creating the memfile.
+#[derive(Clone, Copy, Debug, Default, PartialEq, Eq, Deserialize, Serialize)]
+pub struct GuestMemoryRegionMapping {
+    /// Base host virtual address where the guest memory contents for this region
+    /// should be copied/populated.
+    pub base_host_virt_addr: u64,
+    /// Region size.
+    pub size: usize,
+    /// Offset in the backend file/buffer where the region contents are.
+    pub offset: u64,
+    /// The configured page size for this memory region.
+    pub page_size: usize,
+}
+
 /// Errors associated with the wrappers over KVM ioctls.
 /// Needs `rustfmt::skip` to make multiline comments work
 #[rustfmt::skip]

src/vmm/tests/integration_tests.rs

@@ -212,7 +212,7 @@ fn verify_create_snapshot(is_diff: bool) -> (TempFile, TempFile) {
     let snapshot_params = CreateSnapshotParams {
         snapshot_type,
         snapshot_path: snapshot_file.as_path().to_path_buf(),
-        mem_file_path: memory_file.as_path().to_path_buf(),
+        mem_file_path: Some(memory_file.as_path().to_path_buf()),
     };
 
     controller